1. Field of the Invention
The present invention relates to an apparatus and method of ink jet printing, and more particularly to an apparatus and method of ink jet printing with using ink ejection openings in accordance with the type of a printing medium.
2. Description of the Related Art
Recently, the ink jet printing apparatus has become capable of making a printing in a quality not inferior to the film photograph besides outputting an in-office document through use of mainly a plain paper. This greatly relies upon density increase of the ink jet printing head, droplet size reduction, development of photographic printing medium and evolution of image processing. Meanwhile, image forming is conventionally by use of dye based ink whereas pigmented ink has been recently developed and being used for the purpose of outputting a photograph. The development of pigmented ink allows for improving image substantiality.
In conjunction with the improvement of image substantiality, the ink jet printing apparatuses are now being spread rapidly in the application of producing fine artworks. Fine art refers to a world that a subject matter such as of photograph or painting is printed on an exclusive medium for fine art and the output thereof is exhibited or marketed as an artwork. Accordingly, in producing a fine artwork, there is an importance in the durability not only of ink but also of printing paper.
In order to realize a long-term storage, the printing paper employs a structure having a material, such as a neutral paper or a cotton paper, used as a base material and an ink acceptance layer formed thereon. Furthermore, concave-convex is provided in the surface, to represent a unique texture like a painting paper or canvas. In addition, by increase the paper thickness greater than the existing ink jet paper, paper texture is improved. In this manner, various types of exclusive papers for fine art are under marketing. Specifically, the printing paper available is comparatively thick and elastic, e.g. basis weight ranges from approximately 200 g to approximately 300 g per square meter while paper thickness is from approximately 0.3 mm to 0.5 mm.
Such a fine art paper is ready to produce a paper powder from the paper surface or paper end thereof. Due to this, there is a possibility that the paper powder adheres to the paper feeding roller used in a paper feeding mechanism with a result that a poor paper feed is caused by a reduced friction force. There is also a possibility that a paper powder adheres to the vicinity of an ejection opening of the printing head thus resulting in poor ejection, e.g. ink is not to be ejected, ink ejection is deflected in direction or ink ejection is reduced in amount (hereinafter, referred also to as non-ejection phenomenon). Due to the occurrence of such non-ejection phenomenon, such a stripe as blanked white possibly appears on an image during printing.
In the vicinity of an ejection opening of the printing head, an ink mist caused upon ejection might adhere to the vicinity of an ejection opening besides a paper power, to cause a non-ejection phenomenon through blockage against ejection similarly to the paper powder case. Such a mist includes so-called a floating mist being suspended in the printing apparatus by printing. Besides, there is so-called a splash mist that the ink arrived at a paper surface is splashed and put on a surface of the printing head. In order to remove a paper powder or mist thus adhered to the vicinity of an ejection opening, the existing ink jet printing apparatus is provided with a mechanism that wipes a surface having ejection openings of the printing head. It is a general practice to perform wiping periodically or in proper timing (see Japanese Patent Laid-Open No. H07-164643).
However, because a paper powder frequently leads to a non-ejection phenomenon as compared to a mist when adhered to the vicinity of an ejection opening of the printing head, wiping only is insufficient as a countermeasure. Namely, the mist has a particle size of several μm while the paper powder occurring from a fine-art exclusive paper is in a size of several hundred μm. Non-ejection phenomenon is readily caused by a mere adhesion of one particle of paper powder. Accordingly, there is a need not to produce a paper powder or not to cause a paper powder to soar from a paper surface toward a printing head surface.
In the meanwhile, in the recent ink jet printing apparatus, a plurality of ejection openings are densely arranged in order to realize a quality, high-speed printing, which in many cases employ a printing head arranged with a plurality of ejection openings in a staggered two-array form. However, where performing an ejection of ink at the two arrays of ejection openings at the same time, two arrays of airflows are caused correspondingly to the ejection-opening arrays by the ejection. At this time, by the airflow, pressure is reduced in a space between the two arrays of ejection openings, to cause an airflow soaring in a direction from the paper surface toward the surface having ejection openings of the printing head. This resultingly makes it easy to raise a powder and splashing mist present on the paper surface. Meanwhile, the space between the two arrays of ejection openings is confined by the two arrays of airflows so that the paper powder and mist is placed in a state not easy to escape to the outside. Thus, there is a fear that the paper powder or mist adheres to the surface having ejection openings of the printing head.
In order to avoid the influence of the airflow as caused by a pressure-reduction effect occurring between the two arrays of ejection openings, Japanese Patent Laid-Open No. 2005-288909, for example, discloses an art that changes the array of ejection opening for use is changed in accordance with the printing duty of an image. According to this art, when the printing duty is low, printing is by use of two arrays of ejection openings at the same time. When the printing duty is high, the two arrays of ejection openings are used one array per time, to reduce the influence of the airflow between the two arrays of ejection openings.
However, there encounters a case that it takes uselessly long in printing even where adopting the method described in Japanese Patent Laid-Open No. 2005-288909 in an attempt to relieve the occurrence of paper powder. Namely, according to the method described in Japanese Patent Laid-Open No. 2005-288909, the array of ejection openings for use is indiscriminately restricted at a high print duty regardless of whether a printing medium is ready to cause a paper powder or not ready to cause a paper powder. However, with a printing medium not ready to cause a paper powder, the necessity is low in restricting the array of ejection openings in order to relieve the paper powder because a paper powder is less caused or is slight in amount even if caused even at a high printing duty. Therefore, it is not effective to employ the method described in Japanese Patent Laid-Open No. 2005-288909 where to relieve the paper powder.